Hydrogeochemical Evolution Along Groundwater Flow Paths in the Manas River Basin,Northwest China     

Jianjun Wang  Xing Liang  Yanfeng Liu  Menggui Jin  Peter S.K. Knappett  Yalei Liu 《Ground water》2019,57(4):575-589

The impacts of long-term pumping on groundwater chemistry remain unclear in the Manas River Basin, Northwest China. In this study, major ions within five surface water and 105 groundwater samples were analyzed to identify hydrogeochemical processes affecting groundwater composition and evolution along the regional-scale groundwater flow paths using the multivariate techniques of hierarchical cluster analysis (HCA) and principal components analysis (PCA) and traditional graphical methods for analyzing groundwater geochemistry. HCA classified the groundwater samples into four clusters (C1 to C4). PCA reduced the dimensionality of geochemical data into three PCs, which explained 86% of the total variance. The results of HCA and PCA were used to identify three zones: “recharge,” “transition,” and “discharge.” In the recharge zone the groundwater type is Ca-HCO₃-SO₄ and is primarily impacted by the dissolution of calcite and silicate weathering. In the transition zone the groundwater type is Ca-HCO₃-SO₄-Cl and is impacted by rock dissolution and reverse ion exchange. In the discharge zone the groundwater type is Na-Cl and is impacted by evaporation and reverse ion exchange. In addition, anthropogenic activities impact the groundwater chemistry in the study area. The groundwater type generally changes from Ca-HCO₃-SO₄ in the recharge area to Na-Cl in the discharge area along the regional-scale groundwater flow paths. This study provides a process-based knowledge for understanding the interaction of groundwater flow patterns and geochemical evolution within the Manas River Basin.  相似文献   

外来种福寿螺(Pomacea canaliculata)对3种沉水植物的牧食偏好及水体理化因子的响应     

杨诚  康玉辉  高健  张泽慧  苗滕  廖明军  焦一滢  赵以军 《湖泊科学》2021,33(4):1241-1253

外来种福寿螺(Pomacea canaliculata)相较我国本土螺类其牧食量更大且繁殖速度更快,对栖息地水生植物的现存量和实施水生植被恢复的生态治理工程的成功性可能构成威胁,目前对福寿螺影响浅水湖泊沉水植物的重建缺乏足够的研究.本文通过设置不同沉水植物种类组合系统,研究福寿螺对3种常用于浅水富营养化湖泊治理的沉水植物密刺苦草(Vallisneria denseserrulata)、轮叶黑藻(Hydrilla verticillata)、穗花狐尾藻(Myriophyllum spicatum)的牧食偏好以及不同植物配置系统理化因子的响应变化,结果表明福寿螺对沉水植物植株附着偏好为密刺苦草轮叶黑藻穗花狐尾藻,而牧食破坏强度为轮叶黑藻穗花狐尾藻密刺苦草,轮叶黑藻最容易受到福寿螺牧食影响而快速消亡,穗花狐尾藻叶片也会被全部牧食仅剩下茎,而苦草存活受到的影响较小.福寿螺会导致轮叶黑藻+密刺苦草组合系统中总氮、氨氮、总磷、正磷酸盐浓度显著升高,而密刺苦草+穗花狐尾藻组合中总磷、正磷酸盐浓度显著升高,但是在轮叶黑藻+穗花狐尾藻组合中仅总氮浓度显著升高.研究表明福寿螺能够影响沉水植物间的竞争关系,但是3种沉水植物均不能阻止福寿螺的牧食;福寿螺牧食会显著降低沉水植物生物量,最终会影响草型清水态系统的稳定性.  相似文献   

AntarcticaLC2000: The new Antarctic land cover database for the year 2000     

FengMing Hui  Jing Kang  Yan Liu  Xiao Cheng  Peng Gong  Fang Wang  Zhan Li  YuFang Ye  ZiQi Guo 《中国科学:地球科学(英文版)》2017,60(4):686-696

Antarctica plays a key role in global energy balance and sea level change. It has been conventionally viewed as a whole ice body with high albedo in General Circulation Models or Regional Climate Models and the differences of land cover has usually been overlooked. Land cover in Antarctica is one of the most important drivers of changes in the Earth system. Detailed land cover information over the Antarctic region is necessary as spatial resolution improves in land process models. However, there is a lack of complete Antarctic land cover dataset derived from a consistent data source. To fill this data gap, we have produced a database named Antarctic Land Cover Database for the Year 2000 (AntarcticaLC2000) using Landsat Enhanced Thematic Mapper Plus (ETM+) data acquired around 2000 and Moderate Resolution Imaging Spectrometer (MODIS) images acquired in the austral summer of 2003/2004 according to the criteria for the 1:100000-scale. Three land cover types were included in this map, separately, ice-free rocks, blue ice, and snow/firn. This classification legend was determined based on a review of the land cover systems in Antarctica (LCCSA) and an analysis of different land surface types and the potential of satellite data. Image classification was conducted through a combined usage of computer-aided and manual interpretation methods. A total of 4067 validation sample units were collected through visual interpretation in a stratified random sampling manner. An overall accuracy of 92.3% and the Kappa coefficient of 0.836 were achieved. Results show that the areas and percentages of ice-free rocks, blue ice, and snow/firn are 73268.81 km² (0.537%), 225937.26 km² (1.656%), and 13345460.41 km² (97.807%), respectively. The comparisons with other different data proved a higher accuracy of our product and a more advantageous data quality. These indicate that AntarcticaLC2000, the new land cover dataset for Antarctica entirely derived from satellite data, is a reliable product for a broad spectrum of applications.  相似文献   

Degradation of crude oil in a contaminated tidal flat area and the resilience of bacterial community     

Jaejin Lee  Il Han  Bo Ram Kang  Seong Heon Kim  Woo Jun Sul  Tae Kwon Lee 《Marine pollution bulletin》2017,114(1):296-301

Crude oil spills, Hebei Spirit in South Korea, is considered as one of the worst environmental disasters of the region. Our understanding on activation of oil-degrading bacteria and resilience of microbial community in oil contaminated sites are limited due to scarcity of such event. In the present study, tidal flat sediment contaminated by the oil spill were investigated for duration of 13 months to identify temporal change in microbial community and functional genes responsible for PAH-degradation. The results showed predominance of previously known oil-degrading genera, such as Cycloclasticus, Alcanivorax, and Thalassolituus, displaying significant increase within first four months of the accident. The disturbance caused by the oil spill altered the microbial community and its functional structures, but they were almost restored to the original state after 13 months. Present study demonstrated high detoxification capacity of indigenous bacterial populations in the tidal flat sediments and its resilience of microbial community.  相似文献   

印度洋上层经向翻转环流的冬夏季节对比     

刘雨  徐康  王卫强  谢强  王玉国 《海洋与湖沼》2021,52(5):1104-1114

上层经向翻转环流(shallow meridional overturning circulation, SMOC)主导热带-副热带上层海洋水体交换,对海洋物质输运和热量交换具有重要意义。基于7套海洋再分析数据产品,本文主要探讨了印度洋SMOC的冬夏季节变化及其差异的原因。结果显示,印度洋SMOC主要由南半球副热带环流圈(southern subtropical cell, SSTC)和跨赤道环流(cross-equatorial cell, CEC)组成,并且具有显著的季节差异。夏季风期间, SSTC和CEC均为表层南向输运,表层以下北向输运的逆时针环流结构。冬季风盛行时, SSTC仍维持逆时针结构,但环流中心南移且深度加深,强度弱于夏季;然而, CEC却转向为表层北向输运,表层以下向南输运的顺时针环流结构,其环流中心位置与夏季接近,环流强度与夏季相当。这种印度洋SMOC冬夏结构差异究其原因主要由风生环流主导, CEC冬夏季节环流方向反转是北印度洋冬夏季风转向的结果,而南印度洋信风的季节性位移和强度变化是SSTC强度和位置季节差异的主要原因。  相似文献   

大庆地区地震精定位与震源机制解分析     

张永刚  康健  张天雷 《地震地磁观测与研究》2017,38(2):7-11

依托大庆城市活动断层探测项目,开展大庆区域地震活动性研究。筛选黑龙江省及周边662个地震事件的震相到时,修订研究区域走时模型。对研究区148个地震运用交切法和双差法重新定位,对比发现,双差定位后地震定位精度显著提高,地震空间分布更加集中,条带状更为明显,震源深度表明,研究区孕震层基本位于地壳中上部。利用震源机制解资料,对工作区现代构造应力场进行分析,认为本区域构造应力场主压应力方向为NE向,以水平走滑作用为主。  相似文献   

河南及邻区瑞利波群速度噪声层析成像     

邢康  贾漯昭 《中国地震》2019,35(4):685-694

本文选取河南及邻区39个宽频带和甚宽频带地震台站记录的2014年1月～2015年12月垂直分量的连续波形资料,通过波形互相关和叠加运算得到台站间的经验格林函数,并用时频分析方法提取了498条瑞利波群速度频散曲线,进而采用噪声层析成像方法反演获得了河南及邻区8～25s的瑞利波群速度分布图像。结果表明,8s周期的群速度分布与地表构造特征密切相关,平原地区表现为低速异常,而基岩出露的山区呈现为高速异常;14s、20s周期的群速度在山区表现的高速异常与8s相似,说明中上地壳与地壳浅部结构有一定的相关性和继承性;8～20s周期的群速度在华北平原地区存在低速异常范围随周期增加而减小的现象。华北平原地区在下地壳表现出的低速异常,可能与大陆地壳减薄有关。大致以太行-武陵重力梯度带为界,下地壳表现出的西部低速、东部至研究区中部高速异常差异,体现了地壳东薄西厚的结构特征。  相似文献   

水平分层土层系统等效阻尼比的简化计算方法     

殷琳  楼梦麟  康帅 《震灾防御技术》2019,14(1):10-23

在实际工程场地中,很多土层可视为水平分层,各层土的物理和力学性质存在差异,其中包括土的振动阻尼比。本文讨论水平分层土层系统的等效阻尼比的近似计算方法,基于5个不同的加权函数推导了10种等效阻尼比的计算公式。通过2个算例,分别以等效阻尼比为参数计算水平分层土层的地震反应,并与准确解相比较,分析了不同等效阻尼比近似计算方法的计算精度。数值结果表明,若等效阻尼比计算方法选择不恰当,会导致土层地震反应的计算结果出现较大误差。针对2种不同类型的水平分层土层,建议采用基于三角形分布的加权函数来计算土层系统的等效阻尼比。  相似文献   

Impacts of different vegetation restoration options on gully head soil resistance and soil erosion in loess tablelands     

Mingming Guo  Wenlong Wang  Tianchao Wang  Wenxin Wang  Hongliang Kang 《地球表面变化过程与地形》2020,45(4):1038-1050

Vegetation restoration is identified as an effective approach to control soil erosion and affects soil detachment and resistance to concentrated flow on the Loess Plateau. However, the effects of vegetation restoration at gully heads in loess-tableland remains unclear. This study was performed to investigate the effects of nine vegetation restoration types at gully heads on soil detachment rate (Dr) and soil resistance to concentrated flow (i.e. soil erodibility, K_r and critical shear stress, τ_c). Undisturbed soil samples were collected from nine vegetation-restored lands and one slope cropland (as the control) and were subjected to a hydraulic flume to obtain Dr values of gully heads under six inflow discharges (0.5–3.5 L s^-1). The results showed that the Dr values of nine revegetated gully heads were 77.11% to 95.81% less than that of slope cropland, and the grassland dominated by Cleistogenes caespitosa and the shrubland dominated by Hippophae rhamnoides had a relatively greater decrease in Dr than those of other seven restoration types. The Dr value of nine revegetated gully heads could be better simulated by stream power than by flow velocity and shear stress and was also significantly affected by soil disintegration rate (positively), soil bulk density, saturated hydraulic conductivity, organic matter content, and water-stable aggregate stability (negatively). Additionally, roots with diameters of 0 to 0.5 mm showed a greater effect on Dr than those with larger diameters. Compared to cropland, the nine restored types reduced K_r by 76.26% to 94.26% and improved τ_c by 1.51 to 4.68 times. The decrease in K_r and the increase in τ_c were significantly affected by organic matter content, water-stable aggregate, mean weight diameter of aggregate and root mass density. The combination of grass species (Cleistogenes caespitosa) and shrub (Hippophae rhamnoides) could be considered the best vegetation restoration types for improving soil resistance of gully heads to concentrated flow. © 2019 John Wiley & Sons, Ltd.  相似文献   

Quantitative reconstruction of Holocene sediment sources contributing to the central Jiangsu coast,China: New insights into source-to-sink processes     

Yang Yang  Jianjun Jia  Liang Zhou  Jianhua Gao  Wenhua Gao  Benwei Shi  Zhanhai Li  Ya Ping Wang  Shu Gao 《地球表面变化过程与地形》2020,45(11):2463-2477

Coastal deltaic deposits are the primary locations for sediment storage on Earth, and quantifying their source contributions is a critical prerequisite for delineating S2S patterns in marginal seas. In most cases, quantification for the contribution by fine-grained sediments (i.e. particle size < 63 μm) is considered to be representative to constrain the overall sediment supply. However, this approach may be inappropriate because large differences exist between the two quantities. Here we propose an approach to solve the problem, which is based on the maximum number of tracers from multiple sediment size fractions incorporating the content of all size fractions of sediment. Using this approach, absolute source contributions during the Holocene are reconstructed that provide a first-order model for the S2S pattern of the central Jiangsu coast, China. The Huanghe River is the strongest driver for the Holocene sedimentation, with a mean contribution of ~72 ± 6% (1417 × 10⁸ t). The absolute contributions from the Changjiang and offshore areas were of secondary importance, (i.e. ~17 ± 1% (330 × 10⁸ t) and ~11 ± 5% (217 × 10⁸ t), respectively). The results show that a large difference between the relative and absolute source contributions and the assumption that the relative contribution represents the absolute contribution is invalid in a coastal setting. The impact of the Huanghe is mainly based on episodic events, such as the event of 1128–1855 AD . The model also reveals that the offshore sediments are as important as the Changjiang sediments for the central Jiangsu coast during the Holocene. Thus, the model provides both the time series and overall quantities of sediment supply during the formation and evolution of the Holocene tidal flats on the Jiangsu coast. Our findings shed new light on quantitative analysis of sediment sources applicable to future S2S studies of marginal seas. © 2020 John Wiley & Sons, Ltd.  相似文献